This invention relates to an internal combustion engine and to a method for achieving ignition of fuel in an internal combustion engine.
In an internal combustion engine, in principle, ignition is conventionally achieved either by compression ignition or by spark ignition. One type of compression ignition engine is the so-called dual-fuel engine, in which a gaseous fuel-air mixture is present in the cylinder at the beginning of the compression stroke and ignition is obtained by injecting into the cylinder a liquid fuel, such as diesel oil, having better ignition properties than the gaseous fuel already present in the combustion chamber. A disadvantage of such an arrangement is that the gaseous fuel-air mixture must be sufficiently lean to avoid self-ignition. This limits the pressure that can be achieved in the cylinder before ignition, and consequently also the pressure that is achieved after ignition, as well as the power output provided by the engine.
A disadvantage of spark ignition is that it is necessary to interrupt operation of the engine in order to replace the spark plugs when they reach the end of their useful life.
The known hot bulb engine has previously been used with liquid fuels. In the hot bulb engine, the maximum pressure generated in the cylinder through compression is so low that the temperature of the air is not sufficient to achieve ignition of the fuel injected into the cylinder. The engine is provided with a hot bulb whose interior is in communication with the combustion chamber and which is heated from outside of the cylinder so as to be glowing hot. The fuel in the hot bulb quickly becomes gaseous when it enters the bulb and contacts the hot walls of the bulb, and ignition results. The hot bulb engine is subject to the drawback that it is not possible to control the exact moment of ignition. Moreover, the hot bulb engine has a low power output. For these reasons, the hot bulb engine has become obsolete.